Increase pin limit & add pages like searching

1. Raise the pin limit in DMs to at least 200. Nitro-boosted servers could get increment pin raises (+50, +100, +200?) for boosting levels.

2. Add pages to pins just like in searching. Could display about 10 pins per page? This would be easier for:
-Displaying pins neatly without excessive scrolling
-Making way for having raised pin limits

Here's my bad mockup:

This is a feature that I know a lot of people want, and I don't see any reason against it. Being stuck at only 50 great memories to pin adds up very quickly; this limitation is one of my larger nitpicks about Discord at the moment.